Centrifugal pumps often use multiple vane impellers to pump fluid such as water from an inlet to an outlet. Pump impellers are currently available which have two or more vanes. In order to pass solids through the pump, it is often desirable to utilize a two or three vane impeller. It has been found that existing two and three vane impellers may operate at reduced efficiencies and/or can be unacceptably noisy especially when run at higher speeds in order to generate higher head pressures.
In the most recognized standard two vane impeller design for solids handling the two vanes are normally relatively perpendicular to the shroud. Each vane usually has a constant width of, for example 0.38 inch. In order to pass the required solids the distance between an inlet leading edge of one vane and a trailing edge at the O.D. of the other vane (the space between the two vanes) may be too far apart for “normal/good” hydraulic design. Due to this spacing, the flow transition from an inside surface of the vane to an outside or working side of the vane in the suction region is unstable, especially at flows to the right or left of the “best efficiency point” (BEP). As the flow enters the working side of the vane it dumps into a “void” (open area) that causes the flow to recirculate back to the underside side of the vane. It is believed that these factors reduce the hydraulic efficiency and cause cavitation/noise.